Evaluating agricultural practices
to decrease nitrate leaching
Testing proven and novel practices to decrease nitrate leaching losses from Wisconsin’s cropping systems
Groundwater and surface water are often impacted by elevated nitrate in agricultural regions, and Wisconsin is unfortunately no exception. With a large group of collaborators and stakeholders, we are testing a variety of different traditional and unconventional practices to address nitrate leaching from croplands around the state. Efforts focused on the Central Sands vegetable production region are described here.
Advancing methods of water quality measurement for on-farm research
Deploying a combination of state-of-the-art and lower-cost measurement techniques to evaluate management practices on commercial and research farms
Many farmers and stakeholders are willing to consider changing their management or adopting new practices if they might improve water quality, but directly measuring these benefits remains challenging and often prohibitively expensive. We are testing the potential for lower-cost approaches such as resin lysimeters and strategic soil measurements to evaluate nutrient leaching in on-farm experiments, and are calibrating and validating these approaches using gold-standard methods such as equilibrium tension lysimeters and mesocosms. Study sites include the Wisconsin Integrated Cropping Systems Trial in Arlington, several fields in the Wisconsin Discovery Farms network, and several farmer-led experiments in the Wisconsin Nitrogen Optimization Pilot Program (NOPP). Some of our relevant peer-reviewed papers on this topic include Loper et al. (2024) and Hall et al. (2023).
Expanding the use of “conservation drainage” practices to improve water quality and mitigate greenhouse gas emissions
Coupling tile drainage systems with an array of research-based engineering and conservation practices can improve environmental outcomes while sustaining or increasing farm profitability
Subsurface tile drainage often benefits crop production on poorly drained soils, but drainage can increase nutrient losses to downstream waters. To mitigate these impacts, a wide range of “conservation drainage” practices have been collaboratively developed by researchers and industry stakeholders. Along with collaborators at several Midwestern land grant universities, we are working on several research questions related to these practices, with a particular focus on potential co-benefits of conservation drainage for climate change mitigation. Some of our relevant peer-reviewed papers on this topic include Hall et al. (2023), Lawrence et al. (2021), Yu et al. (2021).
Cropping system diversification to improve water quality, soil health, and climate mitigation
Where and why do perennials and diversified cropping systems impact soil carbon storage and nutrient availability?
Cropping systems that incorporate perennials, animals, cover crops, and extended rotations are often thought to increase the storage of carbon in soil organic matter (aka, “carbon sequestration”). Our work has shown that soil carbon gains are often elusive, but that diversified systems can have critical environmental benefits resulting from increased nutrient retention and recycling. These processes may lead to decrease nitrogen fertilizer requirements, improved water quality, and reduced greenhouse gas emissions. We are collaborating on long-term experiments in Wisconsin and Iowa to address these questions. Some of our relevant papers on this topic include Huang et al. (2025), Ye and Hall (2020), and De et al. (2020).
Advancing measurements to address new questions in agricultural sustainability
New approaches to measure reactive trace gas emissions from soil and water
Soils and waterways are important sources of the trace gases nitrous oxide (N2O) and nitric oxide (NO), which contribute to climate change and air pollution. We have advanced methods to measure the emissions of these gases in the field and lab, including a robust automated chamber method for measuring N2O emissions in very wet soils, where commercially available automated chambers are prone to failure. In a collaborative project with ecosystem modelers, we refined a manual approach for soil NO flux measurements to understand their relationship with tropospheric ozone production and crop yield suppression. Another example of methodological innovation is our fully automated incubation apparatus to measure carbon dioxide fluxes and carbon isotope composition from hundreds of soil cores, which revealed the importance of cover crops in stimulating microbial activity in deep agricultural soils. Representative publications: Lawrence and Hall (2020), Ye and Hall (2020).
Fundamentals of soil organic matter
and soil health measurements
How can we predict the quantity, quality, and beneficial functions of soil organic matter among agricultural and natural soils?
The factors that control the composition, abundance, and beneficial services of soil organic matter remain hotly debated by practitioners and the scientific community. We have used soil samples from Wisconsin farms and sites spanning North America in the National Ecological Observatory Network, to address key unresolved questions about soil organic matter. In particular, we have focused on where, when, and why minerals can protect organic matter vs. stimulating its decomposition. We have also addressed the contentious roles of lignin, a complex plant polymer, in controlling decomposition. Current work focuses on how we can use a key suite of soil characteristics to better predict nitrogen release for plants. Representative publications: Huang et al. (2023), Hall et al., (2022), Yu et al. (2022), Hall et al. (2020).
Redox biogeochemistry, or the unpredictable functions of soggy soils
Where and why do anoxic zones occur in soils, and what are their environmental implications?
Many soils experience zones of oxygen depletion that vary over space and time. Oxygen variability has key implications for the cycling and removal of nutrients through processes such as denitrification, while also controlling the persistence of carbon in soil organic matter and greenhouse gas emissions. Our ongoing work on this topic aims to predict where oxygen limitation occurs, and the practical consequences for water quality and climate mitigation. Representative publications: Chen et al. (2020), Huang et al. (2021, 2020), Huang et al. (2017).